Generalized vitiligo preceded by a generalized figurate erythematosquamous eruption

Segmental and generalized vitiligo: both forms demonstrate inflammatory histopathological features and clinical mosaicism

BACKGROUND

Segmental vitiligo (SV) and generalized vitiligo (GV) are perceived to evolve by different mechanisms, the former with unspecified neural mechanisms and the latter by melanocyte specific autoimmune mechanisms. However, the two diverse mechanisms are difficult to reconcile in cases of "mixed vitiligo". To test the possibility of a common pathogenesis, we reviewed clinical and histopathological features of SV and GV.

MATERIALS AND METHODS

As part of an ongoing histopathological study on vitiligo and vitiligo like lesions, over a 10 year period from 2002 to 2011, biopsies were taken routinely from evolving or recently evolved lesions. 50 cases of SV with quasi-dermatomal distribution and 154 cases of GV were identified and the clinical and histopathological features were compared.

RESULTS

Mild clinical inflammation was recorded in 33 of 154 GV cases but, none among 50 SV had such features. In addition to bilateral symmetrical involvement, mirror image lesions with unusual segmentation were observed in nine cases of GV. SV with a few bilateral lesions (4) and GV with quasi-dermatomal lesions (3), i.e., mixed vitiligo, were included in their corresponding groups for analytical purposes. Focal lichenoid inflammation of varying degrees around epidermal/adnexal melanocytes was identified as a common feature in evolving lesions of both SV (78%) and GV (70%).

CONCLUSIONS

SV and GV demonstrated a similar inflammatory histopathological spectrum. "Segmentation/mosaicism", identified for the first time in GV is another unifying factor. Cutaneous mosaicism harboring fragile melanocyte populations, which are susceptible to external as well as auto-inflammatory mechanisms, is an attractive hypothesis to pursue in the causation of vitiligo.

Transgenic mice expressing IFN-gamma in the epidermis have eczema, hair hypopigmentation, and hair loss

To study the role of IFN-gamma in the pathogenesis of inflammatory skin diseases, we used the involucrin promoter to overexpress IFN-gamma in the suprabasal layers of transgenic mouse epidermis. IFN-gamma mRNA and protein were readily detectable in the skin but not in the blood. Mice exhibited striking hypopigmentation of the hair due to a reduced abundance of DOPA-positive melanocytes. Severely affected mice had reddened skin, growth retardation, hair loss, and flaky skin lesions. Keratinocyte proliferation was increased, and there was epidermal thickening with spongiosis and parakeratosis. Suprabasal beta1 integrin expression and induction of keratin 17 in interfollicular epidermis provided evidence of perturbed differentiation. IFN-gamma receptor expression was reduced, and there was induction of ICAM-1 and MHC class II molecules on the surface of transgenic keratinocytes. The skin of severely affected mice was characterized by a dermal infiltrate of T lymphocytes and macrophages/monocytes, but the epidermis was almost devoid of Langerhans cells and T lymphocytes. The number of Langerhans cells in the lymph nodes was increased in the transgenics, and autoantibodies to keratinocytes were produced. Transgenic mice showed an increased contact hypersensitivity reaction to topical application of DNFB. We conclude that constitutive IFN-gamma expression in the epidermis results in a form of eczema resembling contact dermatitis and in a profound contact hypersensitivity reaction.